1. Technical Field
The present invention relates to a vibrator element, a sensor unit using the vibrator element, an electronic apparatus including the vibrator element and the sensor unit, and manufacturing methods of the vibrator element and the sensor unit.
2. Related Art
Vibration gyro sensors (hereinafter, referred to as “vibration gyros”) have been widely used as angular velocity sensors that enhance body control in vehicles and position detection of car navigation systems, and vibration control and compensation functions (so-called “camera shake compensation”), or the like for digital cameras, digital video cameras, etc. The vibration gyro obtains displacement of an object using a gyro vibrator element of a piezoelectric single-crystal material such as quartz crystal as a highly elastic material by detecting an electric signal generated due to vibration of shaking, rotating, or the like of the object in a part of the gyro vibrator element as an angular velocity and computing a rotation angle.
As vibrator elements used for gyro sensors, piezoelectric vibrator elements (vibration gyro devices) formed using a piezoelectric material such as quartz crystal have been widely used in related art (for example, see Patent Document 1 (JP-A-5-256723)). The vibrator element disclosed in Patent Document 1 is the so-called “tuning-fork piezoelectric vibrator element” including a base part made of quartz crystal and a pair of vibrating arms extended in parallel from one end of the base part. A drive electrode (excitation electrode) that supplies a drive voltage for excitation of the vibrating arm is provided on a principal surface (first surface) of each vibrating arm and a detection electrode is provided on a side surface orthogonal to the first surface. Further, by applying a drive signal (excitation signal) to the drive electrode, the vibrating arm may be vibrated. Here, while the drive signal is applied to the vibrator element for vibration of the vibrating arm in a direction along the first surface (in-plane vibration), when the arm is rotated with the axis in the extension direction of the vibrating arm (for example, the Y-axis in the case of the vibration gyro device including a quartz crystal Z-plate as a base material) as a detection axis, the vibrating arm vibrates in a direction orthogonal to the first surface (out-of-plane vibration) due to Coriolis force. The amplitude of the out-of-plane vibration may be detected as an angular velocity because it is proportional to the rotation velocity of the vibrator element.
The base part and the vibrating arms of the above described vibration gyro device may be integrally formed by etching of quartz crystal using photolithography, for example. Originally, the sectional shape of the vibrating arm is designed to be a rectangular shape, however, it does not become a rectangular shape, but a parallelogram shape, rhombic shape, or more complex indefinite shape due to etching anisotropy of quartz crystal, variations in working process, or the like. In this regard, when the sectional shape of the vibrating arm is deformed from the originally designed rectangular shape, the vibration direction of the vibrating arm shifts from a designed value, and undesired vibration leakage of the so-called “leakage output” occurs and causes deterioration of detection sensitivity of the vibration gyro device. As a method of suppressing the leakage output, a vibration gyro device provided with cut parts near the roots of the vibrating arms to the base part is introduced in Patent Document 2 (JP-A-2008-209215), for example.
The vibration gyro device (angular velocity sensor device) of Patent Document 2 has a base part and a vibrating arm extended from the base part, and a drive electrode that excites vibration in the width direction of the vibrating arm and a detection electrode that detects electric charge due to vertical vibration in the thickness direction of the vibrating arm are provided on the vibrating arm. Further, plural cut parts formed by laser processing are provided near the root of the vibrating arm to the base part at least on one end in the width direction of the vibrating arm. The document describes that the leakage output (oblique vibration) may be suppressed by changing the mass distribution using the cut parts provided near the root of the vibrating arm to the base part.
However, in the vibration gyro device disclosed in Patent Document 2, it is necessary to provide extremely microscopic cut parts for fine adjustment for suppression of leakage output. Recently, there have been problems that it is getting more difficult to form cut parts with downsizing of the vibration gyro device (vibrator element) and the mechanical strength of the vibration gyro device becomes weaker due to the formation of the cut parts.